SmartSMS User Manual
Soft dB inc.
User Manual
p. 113
6. Hum/Buzz problems with the paging system
When connecting external equipment to the SmartSMS unit for paging purposes, it is possible to
create interference and ground loop problems, as it can happen with any electronic equipment
connected together. The SmartSMS unit has an electrical floating ground. If Hum or Buzz problems
are created, there is a few things that can be done to solve them. In any cases, remember that
ground loop problems are all unique and that no universal method can solve all the possibilities.
If you have a faint hum or buzz coming from the paging input and going through the speakers, you
can use the "Paging Priority" function to turn the input OFF when there are no calls. Simply set the
trigger level slightly above the hum/buzz level on input 1 (see figure below) and set the priority to
"OFF if not trigered" in the advanced parameters. This will ensure that the input is OFF, until the
paging signal comes in.
Ground Loop isolator is also recommended on the paging inputs, if you have ground loop problems.
Ground Loop isolator will prevent any DC current to go through the ground conductor and will help
reduce interference between components. These devices are available in many electronic stores
(i.e. Radio Shack).
